1. Field of the Invention
The present invention is directed to hearing aids, and in particular to a hearing aid having a housing worn at the head, and a control device for wirelessly transmitting control signals to the components in the housing.
2. Description of the Prior Art
A number of different versions of hearing aids are known in the art which include a housing adapted to be worn in the ear of a user, and a control device for controlling the functions of the hearing aid such as, for example, volume, which is disposed remote from the housing and which transmits the control signals to the housing without a connecting wire. Such remote control of the functions of the hearing aid is helpful because the current miniaturization capabilities for the housing worn in or behind the ear make it difficult to manually actuate control elements, such as a thumbwheel, located directly at the housing.
A hearing aid system is described in German OS 34 31 584 wherein ultrasound signals are used to transmit information from the control device to the hearing aid housing. The microphone for the hearing aid assumes the function of a receiver element for the ultrasound control signals. A similar device is also described in Austrian Patent 379 929.
It is known from German OS 19 38 381 to use radio waves for transmitting the control signals. This type of apparatus, however, has the disadvantage of being relatively susceptible to disruption. Moreover, difficulties arise relating to the relatively large spectral range of such radio signals, the necessary resonant circuits, and the modulation methods. In this and other systems, it is desirable that the control device be of a size which can be held in the hand, and easily operated. In known systems, the control device necessarily must have a certain size, which makes it difficult for the user to carry conveniently. Moreover, if a person forgets to carry the control device, setting of the volume of the hearing aid is no longer possible.